More than 45 are injured in the assault by uniformed assailants, who set off explosions and exchange fire with bank guards. The purpose wasn't theft but sabotage, a Baghdad security spokesman says.

Smoke rises from the site of a bomb attack in Baghdad. (Mohammed Ameen / Reuters )

Reporting from Baghdad — Armed men wearing police-commando uniforms briefly overran Iraq's Central Bank on Sunday, killing at least 24 people in a brazen daylight assault and sowing panic and confusion in the heart of Baghdad's busiest commercial district.

The corpses of seven more men wearing uniforms and suspected of being among the assailants were found inside the bank after police finally entered, four hours after the assault began. At least 46 people were injured.

Some of the casualties were civilians caught in explosions or gunfire outside the bank, and others were employees trapped inside, police said.

It was the latest in a string of heists targeting banks and jewelers in Iraq, but at least one of the assailants killed himself using an explosives vest, suggesting the motive may have been sabotage rather than robbery.

The attack came on the eve of the long-awaited first gathering Monday of the new parliament, elected in March, and fueled concerns that the continuing failure to choose a new government would lead to more violence. The session, although taking place on schedule, is expected to achieve little as talks on the government's formation are still deadlocked.

The assault exposed the vulnerabilities of the Central Bank, one of Iraq's most vital institutions, and paralyzed the city's commercial center in the middle of a workday afternoon, calling into question the much-touted security gains of recent months.

It began with the arrival of three carloads of gunmen and an explosion outside the bank shortly after 3 p.m. that ignited a generator, sending a huge plume of smoke spiraling over the city. The assailants then stormed the bank, firing automatic weapons.

One group attempted to enter through the front door, where one assailant detonated his vest, and then a second group stormed another entrance, police said. Altogether, witnesses heard four explosions as well as several exchanges of gunfire with the bank's guards.

The gunmen then apparently roamed through the building, though what exactly happened inside was still murky late in the evening. Security forces fearing a hostage scenario ringed the bank, and when they finally entered shortly after 7 p.m., they found only dead and injured bank employees and the seven bodies of suspected assailants.

A police officer at the scene said the group had numbered as many as 20 but that the others had "dissolved into the population as soon as they saw the scale of the police resistance."

According to Maj. Gen. Qassim Atta Moussawi, spokesman for security forces in Baghdad, no apparent attempt was made to steal money, but several floors of the building were set ablaze after the gunmen entered.

"They didn't steal anything," he told the state broadcaster Al Iraqiya. "Their purpose was to sabotage, and though we can't accuse anyone now, the fingerprints of Al Qaeda are very obvious."

The Iraqi government has claimed huge strides in the battle against the extremist Al Qaeda in Iraq organization, with the capture or killing of several of its top leaders. But many Iraqis have been wondering whether — or how — the organization will regroup.